feat: add new flag to allow configuring per pod FQDNs for service source.

[SerjKol80]

What does it do ?

Currently if you create FQDNs for K8S headless services, a service source will generate DNS record for the source. Also, in addition to that, if pods related to that service has a hostname configured, then FQDNs for each pod will also be created.
I.e. if you have service service-1 resulting into FQDN service-1.some.domain there will also be FQDNs like pod-1.service-1.some.domain be generated.

With this change

Fixes #5937

Motivation

I need to generate per pod FQDNs for pods created by Deployment.

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests
• Yes, I updated end user documentation accordingly

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: SerjKol80 / name: Sergey Kolosov (214b916)

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[ivankatliarchuk]

What for? There is FQDN support https://github.com/kubernetes-sigs/external-dns/blob/master/docs/advanced/fqdn-templating.md. Is way more flexible